How programs for this architecture start up the virtual machine.

• §2. Capture startup text
• §3. Set up the Glk objects

§1. VM_Check_Functionality checks that we are running in a Glk interpreter, as well as that it supports the minimum requirements, which are currently that Glk supports unicode, and Glulx supports real numbers. If one of those requirements is not met an error message will be shown before quitting.

[ VM_Check_Functionality res;
    @gestalt 4 2 res; Test if this interpreter has Glk...
    if (res == 0) quit; ...without which there would be nothing we could do

    Set the VM's I/O system to be Glk.
    @setiosys 2 0;

    if (~~glk_gestalt(gestalt_Unicode, 0)) {
        Fatal_Error("This storyfile can only be run in an unicode interpreter.");
    }

    @gestalt 11 0 res; Test if this interpreter supports real numbers...
    if (res == 0) {
        Fatal_Error("This storyfile can only be run in a Glulx interpreter that supports floating-point arithmetic.");
    }
];

[ Fatal_Error msg;
    gg_mainwin = glk_window_open(0, 0, 0, wintype_TextBuffer, GG_MAINWIN_ROCK);
    glk_set_window(gg_mainwin);
    print "Fatal Error: ", (string) msg, "^";
    quit;
];

§2. Capture startup text. It is a semi-common problem for authors to do something which results in text being printed before any Glk windows have been opened, which results in a fatal interpreter error. (Or even worse, an extension is the cause, which the author should not be expected to know the internal details of.) This is very frustrating, as the author often will not know what is the cause of the error as any error messages can't be shown until a Glk window is created; indeed it's often an error message that is trying to be printed, which the author will never see. To help authors, while we wait for the virtual machine to be set up (including a Glk window) we can instead send any text to a memory stream. Then once the VM is ready we can check if any text was sent to the memory stream, and then finally display it in the window. We only capture 256 bytes, which may not be all that is attempted to be printed, but hopefully it gives authors enough to identify the problem.

Constant PRE_STARTUP_TEXT_CAPTURE_MAX_LEN = 256;
Array Pre_Startup_Text_Capture_Buffer -> PRE_STARTUP_TEXT_CAPTURE_MAX_LEN;
Array Pre_Startup_Text_Capture_Results --> 2;
Global Pre_Startup_Text_Capture_Stream;

[ CAPTURE_STARTUP_TEXT_R;
    Pre_Startup_Text_Capture_Stream = glk_stream_open_memory(Pre_Startup_Text_Capture_Buffer, PRE_STARTUP_TEXT_CAPTURE_MAX_LEN, filemode_Write, 0);
    glk_stream_set_current(Pre_Startup_Text_Capture_Stream);
    rfalse;
];

[ END_CAPTURE_STARTUP_TEXT_R len;
    glk_stream_close(Pre_Startup_Text_Capture_Stream, Pre_Startup_Text_Capture_Results);
    len = Pre_Startup_Text_Capture_Results-->1;
    if (len) {
        if (len > PRE_STARTUP_TEXT_CAPTURE_MAX_LEN) {
            len = PRE_STARTUP_TEXT_CAPTURE_MAX_LEN;
        }
        glk_put_buffer(Pre_Startup_Text_Capture_Buffer, len);
    }
    rfalse;
];

§3. Set up the Glk objects.

[ SOUND_CHANNEL_INIT_R;
    if (glk_gestalt(gestalt_Sound, 0)) {
        if (gg_foregroundchan == 0) {
            gg_foregroundchan = glk_schannel_create(GG_FOREGROUNDCHAN_ROCK);
        }
        if (gg_backgroundchan == 0) {
            gg_backgroundchan = glk_schannel_create(GG_BACKGROUNDCHAN_ROCK);
        }
    }
    rfalse;
];

[ OPEN_BUILT_IN_WINDOWS_R res sty;
    gg_mainwin and gg_storywin might already be set. If not, create them.

    if (gg_mainwin == 0) {
        Open the story window.
        Left-justify the header style
        glk_stylehint_set(wintype_TextBuffer, style_Header, stylehint_Justification, 0);
        Try to make emphasized type in italics and not boldface
        glk_stylehint_set(wintype_TextBuffer, style_Emphasized, stylehint_Weight, 0);
        glk_stylehint_set(wintype_TextBuffer, style_Emphasized, stylehint_Oblique, 1);
        gg_mainwin = glk_window_open(0, 0, 0, wintype_TextBuffer, GG_MAINWIN_ROCK);
        if (gg_mainwin == 0) {
            If we can't even open one window, give in
            quit;
        }
    } else {
        There was already a story window. We should erase it.
        glk_window_clear(gg_mainwin);
    }

    if (gg_statuswin == 0) {
        statuswin_cursize = statuswin_size;
        for (sty=0: sty < style_NUMSTYLES: sty++) {
            glk_stylehint_set(wintype_TextGrid, sty, stylehint_ReverseColor, 1);
        }
        gg_statuswin =
            glk_window_open(gg_mainwin, winmethod_Fixed + winmethod_Above,
                statuswin_cursize, wintype_TextGrid, GG_STATUSWIN_ROCK);
    }
    It's possible that the status window couldn't be opened, in which case
    gg_statuswin is now zero. We must allow for that later on.

    glk_set_window(gg_mainwin);
    rfalse;
];